Method of producing biodiesel fuel

ABSTRACT

A method of producing a biodiesel fuel oil, in which all fats or oils having an acid value of 20 or less can be used as a raw material, and in which no wastewater treatment is needed to thereby attain reduction of environmental load, and in which a biodiesel fuel oil conformable to quality standard levels can be obtained. The process for producing a biodiesel fuel comprises the steps of providing a fat or oil having an acid value of 20 or less as a raw material and heating the raw material oil in vacuum to thereby distill off any moistures, odorous substances and free fatty acids; bringing the raw material oil into contact with a hydrophilic adsorbent to thereby adsorb off any remaining free fatty acids and acidic substances; carrying out an ester exchange reaction in the presence of a potassium based alkali catalyst; and purifying light liquid components as a product of ester exchange reaction in accordance with a nonaqueous method.

TECHNICAL FIELD

The present invention relates to a method of producing a high quality fatty acid biodiesel fuel oil with a high inversion rate even from degraded oils and fats such as waste vegetable oils and the like.

BACKGROUND ART

Biodiesel fuel is generally obtained by subjecting vegetable oil and alcohol to an ester exchange reaction to prepare a fatty acid alkyl ester, and used as a diesel combustion fuel. Biodiesel fuel is an oxygenated fuel containing oxygen in its chemical structure, and emits minimal hazardous exhaust gas such as black smoke since it hardly contains any sulfur content. In addition, since biodiesel fuel is plant-derived, the emission of carbon dioxide is counted as zero under the stipulations provided in the Kyoto Protocol. In light of the above, biodiesel fuel is attracting attention as the alternative fuel of light diesel fuel with a low environmental load, and, in Europe and the United States, the standards and legal system for biodiesel fuel have already been established, and more than 5 million tons of biodiesel fuel was produced from soybean oil and rapeseed oil and used in 2005. Meanwhile, in Japan, approximately 10,000 tons of biodiesel fuel is being produced annually from waste vegetable oil and used, in a limited manner, by local authorities and the like. In Japan, a quality standard for biodiesel fuel subject to mixture (B5) of 5% to light diesel fuel has been formulated in January 2007.

It has been conventionally known that a fatty acid alkyl ester can be obtained by subjecting monoglyceride, diglyceride and triglyceride, which are the primary components of oils and fats, and alkyl alcohol to an ester exchange reaction. Meanwhile, it is also known that a fatty acid alkyl ester can be obtained by subjecting free fatty acids and alkyl alcohol to an esterification reaction (for instance, refer to Non-Patent Document 1). Moreover, various studies have been conducted regarding technology for producing a biodiesel fuel oil from oils and fats by using the foregoing reaction. Particularly in recent years, with the economic background of the global oil boom and the like, numerous related patent applications have been filed (for instance, refer to Patent Documents 1 to 11). These Documents attempt to improve the esterification efficiency from various types of raw material oils, and eliminate impurities as much as possible.

Meanwhile, generally speaking, the method of producing a fatty acid alkyl ester-type biodiesel fuel oil can be broadly classified into the following three types.

(1) Homogeneous system, heterogeneous system acid, alkali catalytic reaction (2) High temperature, high pressure uncatalyzed reaction (3) Enzyme reaction

Among the above, the reaction system that is most widely used is the catalytic method of (1). Although methods (2) and (3) are advantageous in that the esterification reaction advances simultaneously together with the ester exchange reaction which does not generate any catalytic residue, the current situation is that the practical application thereof has not yet been realized due to various aspects such as the reaction conversion ratio, initial cost, running cost and the like.

Various types of methods for the catalytic method of (1) have been reported, and can be classified as follows.

[1] Acid catalyst (homogeneous) [2] Acid catalyst (heterogeneous) [3] Alkali catalyst (homogeneous) [4] Alkali catalyst (heterogeneous) [5] Acid catalyst (homogeneous)-alkali catalyst (homogeneous) {two-stage method} [6] Acid catalyst (heterogeneous)-alkali catalyst (homogeneous) [two-stage method] [7] Acid catalyst (heterogeneous)-alkali catalyst (heterogeneous) [two-stage method] [8] Acid catalyst (homogeneous)-alkali catalyst (heterogeneous) [two-stage method]

As the acid catalyst, both homogeneous and heterogeneous systems are used, but as the alkali catalyst, only the homogeneous system has been put into practical use. This is because the conversion ratio is insufficient in other methods.

As described above, the fatty acid alkyl ester-type biodiesel fuel oil has already been strictly standardized in Europe and the United States based on EN14214, ASTM D6751 and so on. However, in the future aiming for 2007, even stricter standards are scheduled to be formulated upon incorporating the opinions of the automotive industry. This movement is a consequential eventuality, and departing from the preferential times as an environmental fuel, this movement perceives the biodiesel fuel oil as the focal point of the alternate fuel of light diesel fuel.

Here, in order to produce a fuel oil that complies with the foregoing standard, a refining step must be provided. Generally speaking, there are two types of alkali catalyst methods as a method of producing biodiesel fuel oil; namely, a washing method and an adsorption method.

If the conversion ratio of ester exchange reaction of the raw material oil is roughly 98%, it is necessary to water-wash and remove residual soap, alcohol, glycerin, salt or glyceride derivative that remain in the order of several thousand ppm (refer to Patent Document 12, etc.). Moisture is subsequently removed by heating the raw material oil. Based on the foregoing water-washing effect, it is highly likely that the glycerin, alcohol and metals (K, Na and the like) can be kept within the range of the regulation value. Nevertheless, with regard to moisture, even if it is thoroughly removed by way of heating and distillation, approximately 500 ppm is the limit. If further heating is performed in order to additionally lower the moisture value, the biodiesel itself may become decomposed during the foregoing refining process. Moreover, a major problem that arises during the washing method is wastewater. Approximately 1 ton to 3 tons of wastewater will arise in order to produce 1 ton of biodiesel fuel oil. However, according to the Act on Prevention of Marine Pollution and Maritime Disaster of 2007, the foregoing wastewater cannot be disposed until it is completely processed, and the consequential cost increase will be enormous.

Meanwhile, although the adsorbent method entails a precondition of being usable only by using a raw material oil in which the free fatty acids are 3000 ppm or less, salts are 5000 ppm or less, and moisture is 1000 ppm or less, and having a conversion ratio of 99% or higher, it is able to refine and produce a biodiesel fuel oil in a quality that is equivalent to or superior than the washing method with respect to impurities other than moisture in the product (refer to Patent Documents 13 to 15, etc.). A significantly different advantage in comparison to the washing method is that the moisture content in the biodiesel fuel oil is extremely low, and that no wastewater will arise.

Nevertheless, when producing a biodiesel fuel oil with the production methods described in the foregoing Patent Documents, depending on the status of the raw material oil before the reaction and that status of the fatty acid alkyl ester after the reaction, it will be difficult to achieve the moisture value of 200 ppm or less, the alcohol value of 1000 ppm or less, and the acid value 0.3 or less as the biodiesel fuel standard values to be set in 2007 onward.

In addition, when giving consideration to the future biodiesel fuel standard and the issue of environmental load, although refining based on the nonaqueous method that does not generated any wastewater is the preferred method, a method of producing a biodiesel fuel oil that is able to constantly achieve the moisture value of 200 ppm or less, the alcohol value of 1000 ppm or less, and the acid value 0.3 or less by using such nonaqueous method does not exist.

Incidentally, the raw materials used in producing a fatty acid alkyl ester-type biodiesel fuel oil is mostly fatty acid glycerol esters, and the production method from such fatty acid glycerol esters primarily used an ester exchange reaction based on alcoholysis. Accordingly, the prevailing reaction is the ester exchange reaction corresponding to [3] alkali catalyst (homogeneous) that uses an alcohol-sodium hydroxide or potassium hydroxide catalyst (for instance, refer to Patent Document 16, etc.).

Nevertheless, it is difficult to obtain fresh vegetable oil or animal oil in which glycerol ester has been refined to 100%, and, pursuant to the increase in demands for biodiesel fuel oil, there is now movement of using defective oils and fats and degraded oils and fats such as waste vegetable oil as the raw material oil. The main impurities of these oils are free fatty acids.

If there is a large amount of free fatty acids in the ester exchange reaction, they will foremost react with alkali metals as the catalyst, and generate alkali soap. Not only will this deteriorate the reaction yield, refining will also become difficult since it also causes emulsion. Accordingly, in the production of a fatty acid alkyl ester fuel based on an ester exchange reaction under an alkali catalyst, it is necessary to control the free fatty acid content in the raw material oil.

If the free fatty acids in the raw material oil are to be converted into fatty acid alkyl ester, the free fatty acids and alcohol must be subject to an esterification reaction. Since the esterification reaction is an equilibrium reaction, the equilibrium is shifted to the product and the yield is thereby increased by excessively using alcohol as one of the raw materials, or removing the water that is created as the side reaction product.

Moreover, in order to accelerate the reaction speed, a catalyst is generally used. Generally speaking, an acidic catalyst is often used for the industrialization process in the esterification reaction of fatty acids. For instance, inorganic acid such as sulfuric acid and phosphoric acid, and organic acid such as p-toluenesulfonic acid are used as the esterification catalyst. Nevertheless, since the foregoing reactions are basically a homogeneous reaction system in which the catalyst exists in the reaction solution in a dissolved state, there is a problem in that it is difficult to separate and collect the catalyst from the product liquid. In addition, as a method for overcoming the foregoing problem, solidification or a solid acid catalyst is often used, and a solid acid catalyst in which sulfonic acid ion-exchange resin or heteropoly acid is supported with silica gel or activated carbon is known. However, when using the foregoing solidification or a solid acid catalyst, although the esterification reaction will sufficiently progress, this alone will result in a low conversion ratio in the ester exchange reaction.

As the esterification method of oils and fats including free fatty acids, there are reports of foregoing [5] acid catalyst (homogeneous)-alkali catalyst (homogeneous) {two-stage method} and [6] acid catalyst (heterogeneous)-alkali catalyst (homogeneous) [two-stage method] in which esterification is foremost performed with an acid catalyst containing a solid acid catalyst, and thereafter performing the ester exchange reaction with an alkali catalyst (refer to Patent Documents 17 to 19, etc.). Nevertheless, the reaction is complex with two catalyst systems that completely differ in property, and the operability is inferior such needing to constantly control the first reaction based on the fatty acid content. Moreover, if the amount of free fatty acids is 20% or more, the profitability from investment in a complex processing plant can be sought. However, if the amount of free fatty acids is, for example, 20% or less, then it will result in overinvestment.

In order to overcome the foregoing problems, the high pressure, high temperature method and the enzyme method have been reported. With the high pressure, high temperature method, it is possible to simultaneously perform the esterification and the ester exchange reaction with the alcohol in a supercritical state (refer to Patent Documents 20 to 25, etc.).

Nevertheless, based on the close examination by the present inventors, the conversion rate is approximately 98% in the esterification reaction of free fatty acids. Thus, ultimate refining is required, and the tendency is for a complex reaction to occur such as the oxidization of the fatty acid moiety under high temperature or the isomerization of the double bond. Moreover, since the apparatus cost is high and the operation is difficult, there is difficulty in the practical application thereof from the perspective of economic efficiency.

In contrast, an esterification reaction using enzymes has also been reported. In the reaction based on lipase, the esterification and the ester exchange reaction will progress simultaneously. Moreover, by stabilizing the lipase on a carrier, the number of cycles can be increased and the production of waste product can be inhibited (refer to Patent Document 26 or 27). Nevertheless, since the foregoing reaction is a biological reaction, problems essentially remain regarding the reaction speed and conversion ratio since the reaction conditions are mild.

In the case of oils and fats in which the amount of free fatty acids is 10% or less (acid value <20) that can be broadly used as the oils and fats as the raw material in the production of a biodiesel fuel oil, foremost, the free fatty acids are removed as impurities, and, after the raw material oil is made to be only the fatty acid glyceride derivative, it is considered to be preferable to implement the ester exchange reaction based on the alkali catalyst method. Nevertheless, the realization of this kind of method is difficult for the following reasons.

Foremost, the method of removing free fatty acids from the raw material oil and fat; that is, the deoxidation method is a method that was established as a refining method in fatty chemistry, and it is possible to remove the free fatty acids in the oils and fats based on the foregoing processing so that the free fatty acid content percentage will be 0.01 to 0.03% (for instance, refer to Non-Patent Document 2, etc.). With this method, the cleaning method based on a weak alkali aqueous solution is generally used. Nevertheless, since alkali waste will arise with this method, costs will be required for processing such alkali waste. In addition, the process becomes difficult since a step of removing the moisture in the oils and fats prior to performing the ester exchange reaction is required after the washing step.

Meanwhile, as the deoxidation method of oils and fats in which the content percentage of unsaturated fatty acids such as palm oil is low; that is, as the deoxidation method of oils and fats having a small iodine number, there is the physical refining method, or the reduced pressure moisture vapor distillation method. This method performs processing under reduced pressure at 200 to 250° C. for 1 to 2 hours. Although this method has high removal efficiency, with oils and fats that contain a large amount of unsaturated fatty acids; that is, oils and fats with a high iodine number (80 or higher), the raw material oil will be limited since dimers will be created and the fatty acid structure will change under the foregoing processing conditions, and it will be unsuitable as an oxidized degraded oil.

Thus, the deoxidation method in general fatty chemistry cannot be used as is as the free fatty acid removal method as the preprocessing of biodiesel fuel production that uses various types of oils and fats and their oxidized degraded oils as the raw material oil.

Moreover, there is also a method of performing heating under reduced pressure prior to reacting waste vegetable oil with alcohol for the purpose of removing moisture and odorous substances in the waste vegetable oil (refer to Patent Documents 28 to 30). However, this method does not refer to free fatty acids. In fact, if the oxidized degraded oils and fats (general waste vegetable oil) of acid value of 5 are processed under the processing conditions (60 mmHg, 84° C.) of Examples of pending patent applications, the free fatty acid content after the processing remained at 1.5% or more (acid value of 3 or higher), and the subsequent reaction conversion ratio also showed a low value at 97.5%. When processing was performed by tightening the conditions (10 mmHg, 180° C.) even further in order to reduce the free fatty acid content, the ratio of the oleic acid, linoleic acid and linolenic acid alkyl ester component as the fatty acid component in the biodiesel as the product decreased, and the reaction conversion ratio was also 97.5%. When processing was performed by further tightening the conditions at 5 mmHg, 200° C., the pour point increased which is considered to be caused by the isomerization from cis to transformer of the fatty acid moiety.

RELATED ART DOCUMENTS Patent Documents [Patent Document 1] Japanese Patent Laid-Open Publication No. 2002-167356 [Patent Document 2] Japanese Patent Laid-Open Publication No. 2002-294277 [Patent Document 3] Japanese Patent Laid-Open Publication No. 2000-44984 [Patent Document 4] Japanese Patent Laid-Open Publication No. 2000-109883 [Patent Document 5] European Patent Application Publication No. 1644470 [Patent Document 6] European Patent Application Publication No. 1616853 [Patent Document 7] European Patent Application Publication No. 1542960 [Patent Document 8] US Patent Application Publication No. 2006/111579 [Patent Document 9] US Patent Application Publication No. 2006/094890 [Patent Document 10] US Patent Application Publication No. 2006/080891 [Patent Document 11] US Patent Application Publication No. 2006/074256 [Patent Document 12] European Patent Application Publication No. 0249463

[Patent Document 13] Japanese Patent Laid-Open Publication No. H10-245586 [Patent Document 14] Japanese Patent Laid-Open Publication No. H10-231497 [Patent Document 15] U.S. Pat. No. 5,972,057 [Patent Document 16] Japanese Patent Laid-Open Publication No. H7-197047 [Patent Document 17] U.S. Pat. No. 6,642,399 [Patent Document 18] U.S. Pat. No. 6,965,044

[Patent Document 19] US Patent Application Publication No. 2004/102640 [Patent Document 20] Japanese Patent Laid-Open Publication No. 2000-109883 [Patent Document 21] Japanese Patent Laid-Open Publication No. 2000-143586 [Patent Document 22] European Patent Application Publication No. 1506996

[Patent Document 23] U.S. Pat. No. 6,187,939 [Patent Document 24] U.S. Pat. No. 6,818,026 [Patent Document 25] U.S. Pat. No. 6,288,251

[Patent Document 26] International Publication No. 01/038553 [Patent Document 27] Japanese Patent Laid-Open Publication No. 2002-233393

[Patent Document 28] Japanese Patent Laid-Open Publication No. H10-245586 [Patent Document 29] Japanese Patent Laid-Open Publication No. H10-231497 [Patent Document 30] U.S. Pat. No. 5,972,057 [Non-Patent Document 1] “Handbook of Organic Chemistry” published by Gihodo, 1988, p 1407 to p 1409 [Non-Patent Document 2] “Introduction to Fatty Chemistry” published by Sangyo Tosho, p 48 to p 49

DISCLOSURE OF THE INVENTION

Thus, in light of the economic efficiency and compatibility with foods, and from a quantitative perspective, an object of the present invention is to provide a method of producing a biodiesel fuel oil capable of using all oils and fats having an acid value of 20 or less, which could be used as the raw material oils and fats of a biodiesel fuel oil, as the raw material, having a low environmental load which does not require wastewater treatment, and capable of complying with the standard value of impurities that arise during the production in the quality standard of 2007 onward.

As a result of intense study in view of the foregoing object, the present inventors discovered that a high quality biodiesel fuel can be produced using oils and fats such as waste vegetable oils having an acid value of 20 or less as the raw material and according to a method with a low environmental load by performing the following steps in a method of producing a biodiesel fuel including a step of subjecting a raw material oil and alcohol to an ester exchange reaction in the presence of an alkali catalyst; specifically, removing moisture, odorous substances and free fatty acids with a hydrophilic adsorbent prior to performing the foregoing ester exchange reaction, using a catalyst containing potassium as the alkali catalyst, refining the reaction product resulting from the ester exchange reaction with a basic substance adsorptive solid adsorbent, and so on, and thereby achieved this invention.

Specifically, the present invention provides a method of producing a biodiesel fuel from a raw material oil having an acid value of 20 or less. This method comprises a step of heating the raw material oil under reduced pressure to distill and remove moisture, odorous substances and free fatty acids, a step of causing the raw material oil to come in contact with a hydrophilic adsorbent to adsorb and remove residual free fatty acids and acidic substances, a step of subjecting the raw material oil and alcohol to an ester exchange reaction in the presence of an alkali catalyst of at least one type selected from a group including potassium hydroxide, potassium carbonate, and potassium alcoholate, a step of separating light liquid components from a reaction product resulting from the ester exchange reaction, and a step of performing, to the light liquid components, processing of causing [the light liquid components] to come in contact with a basic substance adsorptive solid adsorbent, processing of removing solid impurities and the like by way of centrifugation, processing of heating [the light liquid components] under reduced pressure to remove low-boiling substances, and processing of removing solid impurities and the like through a filter.

According to the foregoing method, since moisture, odorous substances and acidic substances such as free fatty acids are removed before the raw material oils and fats are reacted with alcohol, the activity of the alkali catalyst of the ester exchange reaction will not deteriorate. In addition, since it is possible to suppress foreign substances such as large amounts of water, fatty acid alkali soap, and odorous substances from remaining in the fatty acid alkyl ester after the completion of the reaction, the subsequent refining step can also be performed with a method that is of low energy, low cost, and low environmental load, and it is thereby possible to obtain a biodiesel fuel in which the impurity content of moisture, alkali metals, free fatty acids and the like complies with the fuel standard value. Moreover, as a result of the free fatty acids and water being removed prior to the reaction, it is possible to suppress side reactions and the generation of fatty acid soaps resulting from the direction reaction of the free fatty acids. Consequently, emulsion will not be generated easily, and the subsequent gravity separation step of light liquid and heavy liquid can also be performed easily.

In addition, since the removal of the free fatty acids and moisture is performed in two stages; namely, heating under reduced pressure and adsorption with a hydrophilic adsorbent, no problems will arise in the foregoing cleaning method using the alkali aqueous solution, the reduced pressure moisture vapor distillation method, and the heating under reduced pressure processing method.

Moreover, since the light liquid components are refined with the nonaqueous method, the reaction of the light liquid components coming in contact with water and creating soap will not progress, and the problem of wastewater treatment can also be avoided. According to a solid adsorbent column, impurities such as the residual catalyst can be removed easily, and the operability will improve since the steps can be performed continuously; high-density substances such as glycerol, glycerin derivative, and fine adsorbents that remain in trace amounts can be removed with high precision by mandatorily performing gravity separation by way of centrifugation; and according to the heating, depressurization processing, low-boiling substances such as alcohol and water in the light liquid can be thoroughly removed; and aggregated substances and other solid impurities and the like can be removed through a filter. As a result of performing the foregoing processing, it will be possible to produce a biodiesel fuel capable of complying with the fuel standard value regardless of variation in the production steps, and which is compatible in a precision diesel engine based on the common rail method regarding values that are not stipulated as the fuel standard values.

With the method of producing a biodiesel fuel according to the present invention, preferably, the hydrophilic adsorbent is at least one type selected from a group including activated alumina, basic-treated activated carbon, and silica gel.

According to the foregoing hydrophilic adsorbents, from the raw material oil after the heating under reduced pressure processing, acidic impurities such as residual free fatty acids can be removed with high efficiency with a small amount of adsorbent.

With the method of producing a biodiesel fuel according to the present invention, preferably, the ester exchange reaction step includes a step of preparing a catalyst-containing alcohol solution by dissolving the alkali catalyst which is 0.5 wt % to 2.0 wt % in relation [the] raw material oil, in alcohol which is 1.05 to 1.25 molar equivalent in relation to a fatty acid moiety of [the] raw material oil, and a step of mixing and agitating the raw material oil and the catalyst-containing alcohol solution.

As a result of using the foregoing concentration as the alkali catalyst, the catalyst activity in relation to the ester exchange reaction can be sufficiently obtained, and an inversion rate of 98% or more can be achieved with a brief reaction.

Preferably, the foregoing step of separating the light liquid components is performed by subjecting the reaction product to centrifugation. According to centrifugation, in comparison to cases based on the static layer separation method using the difference in specific gravity, the separation can be realized with high efficiency in a short period of time, and continuous operation with other steps is also possible.

Preferably, the foregoing the basic substance adsorptive solid adsorbent is at least one type selected from a group including activated clay, acid clay, activated carbon, bentonite, silica gel, activated alumina, and molecular sieves. According to the foregoing solid adsorbents, the impurities contained in the light liquid can be adsorbed and removed with high efficiency. In particular, since activated clay and activated carbon both have superior dealkalization effect, decolorization effect, and deodorization effect and have a certain degree of fastness, they can be suitably used as the column filler.

Preferably, a pour point depressant and an oxidation stabilizer are added to the light liquid before performing the processing of heating the light liquid components under reduced pressure to remove low-boiling substances. According to the foregoing method, additives such as the pour point depressant and acid value stabilizer will not condense in the biodiesel product, and can be dissolved homogeneously.

With the method of producing a biodiesel fuel according to the present invention, preferably, prior to performing the distillation and removal step, performed are a step of gravity-separating water or an aqueous solution from [the] raw material oil, and a step of removing solid substances from [the] gravity-separated raw material oil with a filter. According to the foregoing preprocessing, the water and aqueous solution in the raw material oil can be removed even further, and the removal of moisture and the like by way of heating under reduced pressure and a hydrophilic adsorbent can be performed even more efficiently.

Preferably, the alcohol used in the ester exchange reaction is at least one type selected from a group including methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, and t-butyl alcohol. According to the foregoing alcohols, the glyceride in the raw material oil and fat will convert into fatty acid alkyl ester at a high conversion rate based on the ester exchange reaction.

With the method of producing a biodiesel fuel according to the present invention, preferably, all of the foregoing steps are performed continuously. According to the foregoing continuous operation, even if there are limitations in the site or space, such site or space can be used to operate a mass production plant. Incidentally, in order to perform all steps continuously, for example, methods such as preparing a plurality of baths to be used in steps that require much time and connecting them with baths to be used in the preceding and subsequent steps, shortening the time by employing the centrifugation method in the various separation steps, and the like may be adopted.

The method of producing a biodiesel fuel according to the present invention preferably includes a step of obtaining glycerin as a by-product. This step specifically includes a step of diluting sulfuric acid or phosphoric acid corresponding to protons of an equivalent mole in relation to an alkali catalyst with water having a molar equivalent of 0.3 to 5 in relation to potassium atoms in [the] alkali catalyst and adding the product to and neutralizing heavy liquid components after [the] light liquid components are separated from the reaction product, and a step of distilling under reduced pressure a filtrate remaining after filtrating and removing the obtained clathrate hydrate, or a hydrated potassium sulphate crystal or a hydrated tripotassium phosphate crystal.

Since heavy liquids contain most of the catalyst that was used in the reaction in addition to the glycerin as the primary component, in order to be used as fuel, generally speaking, a special boiler is required for alkali corrosion, and, when distillation under reduced pressure is performed, polyglycerol is generated, and the distillation yield is 50% or less. Moreover, if general neutralization that uses acid is performed, this will result in a high viscosity slurry or semisolid, and the filtration and removal of salt and the distillation operation will become extremely difficult. Nevertheless, according to the method of the present invention, since the salt after neutralization will take on a large crystal structure as a water-containing crystal of acid potassium salt, the acid potassium salt can be promptly separated, and the system will not become high viscosity, whereby filtration and removal can be easily performed. The subsequent distillation process can also be performed easily, and high purity glycerin can be obtained at a high yield.

With the method of producing a biodiesel fuel according to the present invention, since the ester exchange reaction in the presence of an alkali catalyst is performed after removing moisture, odorous substances and free fatty acids from the raw material oil as much as possible and the product after the reaction is refined with the nonaqueous method, degraded oils and fats having an acid value of 20 or less can be used as the raw material, and it is possible to produce a biodiesel fuel oil having a low environmental load since it does not require wastewater treatment, and capable of complying with the standard value of impurities that arise during the production in the quality standard of 2007 onward.

BEST MODE FOR CARRYING OUT THE INVENTION

The preferred embodiments of the present invention are now explained.

(Method of Producing Biodiesel Fuel)

With the method of producing a biodiesel fuel according to the present invention, oils and fats having an acid value of 20 or less are used as the raw material. So as long as the acid value is 20 or less, any kind of oil or fat may be used, and, for instance, vegetable oils and fats such as rapeseed oil, soybean oil, palm oil, palm kernel oil, sunflower oil, rice oil, sesame oil, corn oil, coconut oil, sunflower oil, safflower oil, peanuts oil, cotton seed oil, linseed oil, and mustard oil, and animal oils and facts such as beef fat, lard, whale oil, and fish oil, or their waste vegetable oil, or the degraded oils and the like that arise from the production process of the foregoing animal and vegetable oils can be used. If the acid value exceeds 20, this will mean that the free fatty acid components will be contained at 10% or more, and the production efficiency will deteriorate, and problems will arise from the perspective of economic efficiency. Moreover, although there will be no problem even if impurities such as water and the like get mixed in, it is preferable to properly determine the amount of impurities to be within the bounds of common sense as the starting raw material.

With the method of producing a biodiesel fuel according to the present invention, prior to performing the ester exchange reaction, performed are a step of heating the raw material oil under reduced pressure to distill and remove moisture, odorous substances and free fatty acids, and a step of causing the raw material oil to come in contact with a hydrophilic adsorbent to adsorb and remove residual free fatty acids and acidic substances.

The foregoing distillation and removal step is preferably performed at 50 to 170° C., and 1 to 20 mmHg. If the temperature is less than 50° C., hardly any vapor pressure can be ensured, whereby the removal efficiency will become inferior. Meanwhile, if the temperature exceeds 170° C., the unsatured portion in the fatty acid moiety will become degenerated, and there will be an adverse effect on the property as the biodiesel fuel oil. Moreover, the apparatus cost and operating cost will increase in order to maintain the high-vacuum state of less than 1 mmHg, and if the pressure exceeds 20 mmHg, moisture can be removed but the most of the free fatty acids will remain.

Here, the raw material oil may be heated by performing heat exchange with the moisture vapor in the heat exchanger. Since the surface area can be increased by introducing the heated raw material oil into the decompressor in an atomized state, this is preferable since the evaporation speed of the moisture and free fatty acids can be accelerated. The raw material oil that passed the foregoing step can have, for instance, a moisture value of 500 ppm or less, a free fatty acid content of 5000 ppm or less, and odorous substances of 500 ppm or less.

In the foregoing adsorptive removal step using the hydrophilic adsorbent, as the adsorbent, it is preferable to use at least one type selected from activated alumina, basic-treated activated carbon, and silica gel having a grain size of 0.1 μm to 10 μM. The adsorbent is preferably used by being filled in a column, and the fill amount of the adsorbent can be a small amount of approximately 0.1% to 5.0% of the raw material oil to be processed. If the fill amount is less than 0.1%, the acidic substances such as free fatty acids cannot be sufficiently removed up to a prescribed amount. However, if the fill amount exceeds 5%, the adsorbed amount of the raw material oil will decrease and the adsorbent itself will affect the production cost. The raw material oil that passed through this column can be reduced, for example, to have a free fatty acid content of 0.3% or less. With the foregoing amount, for instance, if 1% of potassium hydroxide is used as the catalyst in relation to the raw material oil, the amount that will be consumed as fatty acid soap can be suppressed to less than 10% of the catalyst content, and the reaction liquid concentration of the generated fatty acid soap will be lower than the CMC (Critical Micelle Concentration). Thus, most of the generated soap will dissolve in the heavy liquid (glycerin layer) after the gravity separation, the impurity content in the light liquid will decrease, and the refining process is thereby facilitated. If this step is omitted and reaction is performed with the same catalyst content with a free fatty acid content of 0.5%, 10% or more of the catalyst will be converted to soap and consumed, the reaction conversion efficiency will decrease and become higher than the CMC concentration. Thus, separation after the reaction will be difficult, and the refining process will also become difficult since the soap concentration in the light liquid will increase.

With the method of producing a biodiesel fuel according to the present invention, subsequently, the raw material oil and alcohol are subject to an ester exchange reaction in the presence of an alkali catalyst.

The alcohol to be reacted with the raw material oil is selected from at least one type selected among methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, and t-butyl alcohol. The purity of the alcohol is desirably 99.5% or higher.

As the alkali catalyst, a potassium series basic catalyst such as potassium hydroxide, potassium carbonate, potassium alcoholate or the like is used. In comparison to a sodium series basic catalyst such as sodium hydroxide, for instance, if methanol having a purity of 99.8% is used as the alcohol in an amount that is equivalent to 1.10 of the stoichiometric amount, the catalyst content is set to be 1 wt % of the raw material oil, and an ester exchange reaction is performed at 64° C. with a raw material oil having a moisture content of 0.05% and a free fatty acid content of 0.3%, whereas with potassium hydroxide it took less than 5 minutes to reach the conversion ratio of 99% or more, with sodium hydroxide, it finally reached 97.5% after the lapse of 2 hours, and the conversion ratio did not thereafter improve. Moreover, even in the gravity separation of light liquid and heavy liquid after the reaction, whereas with potassium hydroxide the interface clearly appeared after approximately 20 minutes, with sodium hydroxide, cloudy emulsion existed in the vicinity of the interface even after the lapse of 8 hours, and a clear interface did not appear. The foregoing phenomena are due to the difference in the catalyst activity and because the CMC of the sodium soap is lower in comparison to the potassium soap.

With the method of producing a biodiesel fuel according to the present invention, preferably, a catalyst-containing alcohol solution is foremost prepared, and the raw material oil and the catalyst-containing alcohol solution are subsequently mixed and agitated. Consequently, the ester exchange reaction can be completed in an extremely short period of time.

Here, the amount of catalyst to be dissolved in the alcohol is preferably 0.5 to 2.0 wt % in relation to the raw material oil, and more preferably 0.7 to 1.5 wt % Moreover, the additive amount of alcohol in relation to the raw material oil is preferably 1.05 to 1.25 molar equivalent of the stoichiometric amount, and more preferably 1.08 to 1.15 molar equivalent. The greater the additive amount of catalyst within the foregoing prescribed range, the faster the conversion speed and conversion ratio. However, if the additive amount of catalyst exceeds the given range, the equilibrium inversion rate becomes constant, and contrarily facilitates the reaction of generating soap. The greater the additive amount of alcohol within the foregoing prescribed range, the faster the conversion speed and conversion ratio. However, if the additive amount of alcohol exceeds the given range, the equilibrium inversion rate becomes constant, and the excess alcohol will be wasted. In addition, the specific gravity of the heavy liquid glycerin layer in the gravity separation after the reaction will decrease due to the alcohol, and since the alcohol itself will develop a function as the interface activator, the gravity separation tends to become difficult.

During the preparation of the catalyst-containing alcohol solution, in order to prevent the alcohol from bumping due to the local overheating caused by the heat of dissolution of the catalyst, preferably, a prescribed amount of alcohol is placed in the dissolution bath beforehand, and, while sufficiently agitating the dissolution bath, placing small amounts of catalyst at a time to completely dissolve the catalyst. Moreover, in order to discharge the heat of dissolution, preferably, cooling water is caused to flow in the cooling water jacket so as to maintain the system temperature to be less than the alcohol boiling point.

The reaction of the raw material oil and alcohol is preferably performed at 25° C. to 250° C., and more preferably 50° C. to 100° C., and the pressure is preferably an atmospheric pressure of 0.1 MPa to 7.8 Mpa, and more preferably an atmospheric pressure of 0.1 MPa to 2.0 MPa. Under the foregoing conditions, the equilibrium inversion rate will reach 99.8% or more. Since the reaction of triglyceride and alcohol is a reversible reaction, it is necessary to set the optimal reaction temperature and pressure in order to maximize the equilibrium inversion rate. Nevertheless, if the temperature is raised to be higher than the alcohol boiling point in order to accelerate the reaction speed, since the reactor is a pressure vessel, there will be disadvantages in terms of cost. Accordingly, the setting of the optimal temperature and pressure will be in the vicinity of the boiling point of the alcohol to be used and within the range of ordinary pressure to 0.12 MPa. Moreover, the reaction time should be set to the shortest time possible. This is because, as described above, the reaction is a reversible reaction, and the generated fatty acid alkyl ester will react with the residual water and cause a side reaction of hydrolysis. Accordingly, the reaction time is optimally set to 1 minute to 20 minutes.

The reaction product of the ester exchange reaction of the raw material oil and alcohol is a mixture having fatty acid alkyl ester and glycerin as its primary components. These components respectively have a density of approximately 0.87 to 0.90 gcm³ and 1.10 to 1.25 g/cm³, and, since their mutual solubility is also great, the light liquid having fatty acid alkyl ester as its primary component and the heavy liquid having glycerin as its primary component are separated by being left at rest for a prescribed time or by way of centrifugation. As a result of subjecting the heavy liquid to neutralization/distillation processing, glycerin can be obtained as the by-product. Since the light liquid part includes impurities such as trace amounts of catalyst, fatty acid soap, unreacted alcohol, odorous substances and the like, refining is further performed.

With the method of producing a biodiesel fuel according to the present invention, the refining of the light liquid components is performed according to a nonaqueous method; that is, a method that does not including a water-washing step. Specifically, performed are, to the light liquid components, processing of causing [the light liquid components] to come in contact with a basic substance adsorptive solid adsorbent, processing of removing solid impurities and the like by way of centrifugation, processing of heating [the light liquid components] under reduced pressure to remove low-boiling substances, and processing of removing solid impurities and the like through a filter. Although the foregoing processing steps are preferably performed in the order indicated above, they are not limited to said order, and may be interchanged as needed.

The processing of causing the light liquid components to come in contact with the solid adsorbent is the processing that uses a solid basic substance adsorbent, and can be performed, for example, by passing the light liquid components through a basic substance removal adsorbent filled column. As the adsorbent, used may be at least one type selected from a group including activated carbon, activated carbon fiber, activated clay, acid clay, bentonite, diatom earth, activated alumina, molecular sieves and silica gel. These adsorbents may be subject to microwave processing and thermal processing (150° C. to 700° C.) immediately before being used. Here, the grain size of the filler is preferably within the range of 0.01 mm to 1.0 mm. The adsorption efficiency will be more favorable if the grain size is smaller, but if it is any finer, the pressure loss during the passing of the column will be great and the time required for passing through the column will be long. Moreover, if the grain size is 1.0 mm or larger, a sufficient adsorption effect cannot be obtained. The amount of filler will suffice if it is 0.5 wt % to 2.0 wt %, but more filler may be filled. The spent filler can be treated by way of recycling or disposal. The transit speed may be set, for example, to approximately 5 to 30 liters per minute, and, if solid-liquid centrifugation processing is to be subsequently performed, it may be adjusted to the centrifugation processing performance. The potassium concentration of the light liquid components after the solid adsorbent processing will be, for instance, 5 mg/kg or less. The liquid is neutral.

Moreover, the processing of removing solid impurities and the like from the light liquid components by way of centrifugation is performed, for example, with a solid-liquid separation centrifugal separator. As a result of performing the foregoing processing, fillers of 1 μm or less and high-density substances such as trace amounts of residual glycerin and glycerin derivative can be removed.

Incidentally, if it is necessary to add additives such as the pour point depressant and the oxidation stabilizer, these are preferably added with a static mixer or the like at this time.

Moreover, the processing of heating the light liquid components under reduced pressure is performed for removing low-boiling substances, and is performed, for instance, within a vacuum tower comprising functions such as reduced pressure dehydration, deodorization, deoxidation and so on. Preferably, the pressure is 1 to 100 mmHg, and the temperature is 20 to 100° C. According to the foregoing processing, for instance, the moisture in the light liquid will be 0.02% or less, the free fatty acid content will be 0.15% or less, the alcohol content will be 0.1% or less, the solid substance will be 0.005% or less, and the odorous substances will be 10 ppm or less.

Moreover, the processing of removing solid impurities and the like through a filter can be performed, for instance, using a cartridge-type filter or the like in order to remove particulates and condensed substances of 1 μm or larger.

With the method of producing a biodiesel fuel according to the present invention, prior to performing the step of heating the raw material oil under reduced pressure to distill and remove moisture, odorous substances and free fatty acids, a step of gravity-separating water or an aqueous solution from [the] raw material oil, and a step of removing solid substances from [the] gravity-separated raw material oil with a filter may also be performed. The gravity separation step is performed, for example, leaving it at rest for approximately 4 to 12 hours, and, in order to constantly maintain the raw material oil in a liquid state, the processing is preferably performing by heating as needed. Consequently, the fine solid content, moisture, salts, high-density organic content and the like contained in the raw material oil can be deposited and removed, and, as a result of removing supersaturated water, the moisture value in the raw material oil can be made to be, for instance, 10000 ppm or less. The filter removal step can be performed by passing the solid substances through a strainer equipped with a cartridge filter of 100 to 1000 mesh. According to this step, the fine solids can be removed even further and, for instance, the solid content can be made to be 0.05% or less.

With the method of producing a biodiesel fuel according to the present invention, preferably, all of the foregoing steps are performed continuously. By preparing a plurality of apparatuses for performing the same step as needed, biodiesel fuel can be produced efficiently without wasting time.

According to the method of producing a biodiesel fuel of the present invention, since the ester exchange reaction in the presence of an alkali catalyst is performed after removing moisture, odorous substances and free fatty acids as much as possible from the raw material oil, and the product after the reaction is refined with the nonaqueous method, it is possible to produce a high quality biodiesel fuel from degraded oils having an acid value of 20 or less such as animal and vegetable oils and waste vegetable oil by way of an ester exchange reaction with alcohol using a catalyst, and which complies with the public biodiesel standards such as EN14214 and ASTMD6715.

Incidentally, a biodiesel fuel that complies with the reference values provided in EN14214 and ASTMD6715 means the biodiesel fuels that have the following properties: density of 0.860-0.900 g/cm³, kinetic viscosity of 3.5-5.0 mm²/s, flash point >120° C., cetane number >51, moisture <500 ppm, acid value <0.5 mgKOH/g, alcohol content <0.20%, ester content >96.5%, total glycerol content <0.25%, and alkali metals content <5 mg/kg, and which can be used as diesel vehicle fuel. Moreover, from 2007 onward, the standard values are scheduled to be even stricter as follows: moisture <200 ppm, alcohol content <1000 ppm, acid value 0.3 mgKOH/g, and ester >98.5%. However, according to the method of producing a biodiesel fuel of the present invention, it is possible to obtain a diesel fuel that satisfies the foregoing standards as a result of using raw material oil in which the acid value does not exceed 20.

With the method of producing a biodiesel fuel according to the present invention, glycerin can be obtained as the by-product from the heavy liquid components of the reaction product after the ester exchange reaction. Foremost, sulfuric acid or phosphoric acid is delivered in droplets to the heavy liquid component in order to neutralize the alkali catalyst. Preferably, acid corresponding to the protons in the molar equivalent of the alkali catalyst is diluted with water having a molar equivalent of 0.3 to 5 in relation to the potassium atoms in the alkali catalyst and delivered in droplets. Moreover, preferably, the reaction is performed while cooling since the temperature of the neutralization buffer will increase due to the heat of neutralization. After the delivery in droplets is complete, for example, agitation is performed for 5 to 20 minutes, and the agitation is thereafter stopped and left still for 30 minutes. After the crystal of the acid potassium salt is deposited, it is filtered and removed, and the obtained filtrate is distilled. Preferably, the distillation is performed at 1 mmHg to 20 mmHg, and 160° C. to 190° C. If the temperature is any higher, the glycerin will decompose. After the distillation, the light liquid having fatty acid alkyl ester as its primary component and the heavy liquid having glycerin as its primary component are separated by way of centrifugation. Consequently, it is possible to obtain glycerin having a purity of 99% or higher. The light liquid that was obtained by way of centrifugation is once again subject to refining by the solid adsorbent processing and the like, whereby biodiesel fuel can be obtained therefrom.

(Biodiesel Fuel Production Apparatus)

An example of a production that is able to implement the foregoing method of producing a biodiesel fuel according to the present invention is now explained with reference to the attached drawings.

The biodiesel fuel oil production apparatus to implement the method of producing a biodiesel fuel according to the present invention may include, as shown in FIG. 1, a pretreatment unit 1, a dehydration-deodorization-deoxidation unit 2, an acidic substance removal unit 3, a catalyst-containing alcohol solution preparation unit 4, a mixed reaction unit 5, a liquid-liquid separation unit 6, a neutralization/distillation processing unit 7, a basic substance adsorption processing unit 8, a high density substance removal processing unit 9, a low-boiling substance removal processing unit 10, and a particulate/condensed substance removal processing unit 11. Incidentally, FIG. 2 shows the configuration of the pretreatment unit 1, the dehydration-deodorization-deoxidation unit 2, and the acidic substance removal unit 3, FIG. 3 shows the configuration of the catalyst-containing alcohol solution preparation unit 4, the mixed reaction unit 5, and the liquid-liquid separation unit 6, FIG. 4 shows the configuration of the basic substance adsorption processing unit 8, the high density substance removal processing unit 9, the low-boiling substance removal processing unit 10, and the particulate/condensed substance removal processing unit 11, and FIG. 5 shows the configuration of the neutralization/distillation processing unit 7, respectively.

The pretreatment unit 1 comprises, as shown in FIG. 2, a raw material oil reception tank 13 including a stainless net of roughly 10 to 100 mesh at the reception opening, a raw material oil storage tank 14 that is tapered toward the lower part, and a liquid-liquid centrifugal separator 15 and a strainer with cartridge filter 17. The raw material oil is foremost placed in the raw material oil reception tank 13 upon passing through a stainless net of 10 to 100 mesh. Here, the relatively large solid substances contained in the waste vegetable oil and the like are removed with the mesh. The raw material oil reception tank [13] is provided with steam or a heating wire capable of heating up to roughly 50° C., and is able to handle oils and fats such as palm oils and animal oils that have a high solidifying point in liquid form even during operation in the cool seasons of 0° C. or less.

Subsequently, the raw material oil is fed into the raw material oil storage tank 14 via a feed pump. The raw material oil is left at rest in the raw material oil storage tank 14 for 4 hours to 12 hours. Consequently, the fine solid content, moisture, salts, high-density organic content contained in the raw material oil are deposited, and removed from the lower drain valve. Based on the foregoing physical gravity separation, the supersaturated water is removed, and the moisture value in the raw material oil can be reduced, for instance, to 10,000 ppm or less. The supernatant solution after the removal is passed through the strainer 17 and fed into the dehydration-deodorization-deoxidation unit 2. In order to continuously perform the operation of the pretreatment unit 1, as shown in FIG. 2, preferably, a plurality of raw material oil storage tanks 14 are prepared to enable constant feeding to the subsequent step in consideration of the standing time. Moreover, the primary property values of oils that will affect the properties of the biodiesel fuel such as the iodine number and average molecular weight are prepared, the present invention can also be used suitably in cases of mixing heterogeneous oils. Moreover, the raw material oil storage tank 14 is provided with steam or a heating wire capable of heating up to roughly 50° C. It is thereby possible to handle oils and fats such as palm oils and animal oils that have a high solidifying point in liquid form even during operation in the cool seasons of 0° C. or less.

In order to further feed the raw material oil to the subsequent step continuously, a centrifugal separator 15 is provided. Consequently, the standing effect; that is, since the fine solid content, moisture, salts, and high-density organic substances can be removed in a short period of time, the steps can be performed in further continuity. The raw material oil that was subject to the foregoing primary processing is passed through the strainer 17 comprising a cartridge filter of 100 to 1-000 mesh in order to further eliminate fine solids, whereby obtained is a preprocessed raw material oil having, for instance, a solid content of 0.05% or less.

The dehydration-deodorization-deoxidation unit 2 comprises a steam generation boiler 19 capable of using a biodiesel fuel oil and glycerin as fuel, a multitubular heat exchanger 18, a reduced pressure dehydration-deodorization-deoxidation tower 20, a condenser 22, and a vacuum pump 23.

The raw material oil from which solid substances were removed with the pretreatment unit 1 is fed into the multitubular heat exchanger 18 with a feed pump, is subject to heat exchange with moisture vapor during the passage through the multitubular heat exchanger 18, and heated to a temperature that is required in the subsequent reduced pressure dehydration-deodorization-deoxidation tower 20. The created raw material oil passes through the dispersion nozzle provided to the reduced pressure dehydration-deodorization-deoxidation tower 20 and sprayed within the tower. The sprayed raw material oil, in a film state, passes above a plurality of fin-shaped perforated plates provided within the tower. Specifically, in a state where the surface area has increased due to the effect of spraying and perforated plates at 20 mmHg or less and a temperature of 50° C. to 170° C., moisture, odorous components, and free fatty acids will promptly evaporate, be discharged from the upper exit of the tower 20, and thereafter removed outside the system after being formed into a coolant with the condenser 22. Consequently, the raw material oil will be dehydrated, deodorized and deoxidized so as to have a moisture content of 0.05% or less, odorous substances of 0.05% or less and free fatty acid content of 0.5% or less.

The acidic substance removal processing unit 3 comprises a solid hydrophilic adsorbent filled column 21. Acidic substances such as free fatty acids remaining in the raw material oil that passed through the reduced pressure dehydration-deodorization-deoxidation tower 20 is further removed through adsorption with a hydrophilic and basic solid adsorbent. With the removal conditions of the reduced pressure dehydration-deodorization-deoxidation tower 20 that were set in order to prevent the thermal degradation of the fatty acid moiety, although the total free fatty acid content can only be reduced up to roughly 0.5% since only a part of the free fatty acids of C18 or higher can be removed, by passing it through the acidic substance removal processing unit 3, the foregoing free fatty acids can also be removed, and the free fatty acid content can be removed up to 0.3% or less. With the foregoing amount, for instance, if 1% of potassium hydroxide is used as the catalyst in relation to the raw material oil, the amount that will be consumed as fatty acid soap can be suppressed to less than 10% of the catalyst content, and the reaction liquid concentration of the generated fatty acid soap will be lower than the CMC (Critical Micelle Concentration). Thus, most of the generated soap will dissolve in the heavy liquid (glycerin layer) after the gravity separation, the impurity content in the light liquid will decrease, and the refining process is thereby facilitated. If this step is omitted and reaction is performed with the same catalyst content with a free fatty acid content of 0.5%, 10% or more of the catalyst will be converted to soap and consumed, the reaction conversion efficiency will decrease and become higher than the CMC concentration. Thus, separation after the reaction will be difficult, and the refining process will also become difficult since the soap concentration in the light liquid will increase.

The catalyst-containing alcohol solution preparation unit 4 comprises, as shown in FIG. 3, a catalyst dissolution bath 27 including a cooling water jacket, and an alcohol storage tank 29. The preparation of the catalyst-containing alcohol solution is performed with a batch method according to the ester exchange reaction. Foremost, a prescribed amount alcohol is fed from the alcohol storage tank into the catalyst dissolution bath 27 with a feed pump 16. Subsequently, while agitating the bath, a prescribed amount potassium series catalyst is introduced through a shooter at the upper part of the dissolution bath until it is completely dissolved. Here, since the heat of dissolution will arise, preferably, cooling water is caused to flow in the cooling water jacket to prevent the series from become 65° C. or higher. As a result of dissolving the catalyst in the alcohol in advance, the ester change reaction with the raw material oil can be completed in an extremely short period of time. If the catalyst-containing alcohol solution is not prepared in advance and the alcohol and catalyst are placed directly into the raw material oil and reacted, it took 30 minutes to achieve a 96% conversion rate, and ultimately the conversion ratio only improved up to 98.5%, and this took 2 hours.

The mixed reaction unit 5 comprises an agitation reaction tank 24 configured from an agitation motor 25 and an agitating blade 26. The agitation reaction tank 24 is a cylindrical reactor, and an agitating blade 26 is mounted on a rotating shaft that is disposed in the center thereof. As a result of agitating this rotating shaft at a prescribed speed with the agitation motor 25, the raw material oil and the catalyst-containing alcohol can be promptly caused to come in contact and react. Moreover, in order to adjust the reaction temperature to a prescribed temperature of 50 to 65° C., a jacket and a heater and the like capable of cooling and heating are provided to the agitation reaction tank [24]. Two or more agitation reaction tanks 24 may be prepared so that the subsequent step onward will be performed continuously to realize a sequential and alternate reaction. Since the time required for the overall reaction is less than 30 minutes, the continuity can be maintained even with one agitation reaction tank 24.

The liquid-liquid separation unit 6 is configured from a static specific gravity separator 30 and a liquid-liquid separation centrifugal separator 40. The reaction liquid after the reaction if fed into the static specific gravity separator 30 while maintaining the temperature to 50° C. or higher, and left at rest for 2 hours to 8 hours and returned to room temperature (15 to 25° C.). Consequently, the light liquid part (fatty acid alkyl ester liquid part) and the heavy liquid part (glycerin liquid part) will be separated. The static specific gravity separator 30 is provided with a transparent window portion at a prescribed position to allow the confirmation of the liquid-liquid interface. After the interface clearly appears, the heavy liquid is extracted from the drain provided at the bottom of the static specific gravity separator 30. Although the opening and closing of the drain cock can be performed manually by visual judgment of the liquid state, in the present invention it is automatically controlled with an interface sensor. The heavy liquid is fed into the neutralization/distillation processing unit 7. After the heavy liquid has been extracted, the light liquid part is fed into the basic substance adsorption processing unit 8. In order to continuously perform the steps, a plurality of separation layers 30 may be provided, or the reaction product can be directly introduced from the agitation [reaction] tank 24 to the liquid-liquid separation centrifugal separator 40 in order to separate the light liquid and the heavy liquid.

The basic substance adsorption processing unit 8 comprises, as shown in FIG. 4, a basic substance removal adsorbent filled column 31. While the light liquid that was fed into the liquid-liquid separation unit 6 passes through the column 31, the contained basic substances such as the fatty acid soap and alkali catalyst are eliminated by way of adsorption. A part of the hydrophilic substances such as the trace amounts of residual water, glycerin, and coloration substances are also eliminated. Preferably, the column 31 is also prepared in a plurality so that the operation can be continuously performed during the replacement of the filler. The spent filler can be recycled or disposed. The transit speed can be adjusted to match the speed of the adsorption effect or subsequent processing, but preferably it is set to approximately 5 to 30 liters per minute. The speed can be accelerated even further by using the buffer tank and the centrifugal separator in parallel.

The high density substance removal processing unit 9 comprises a solid-liquid, liquid-liquid separation centrifugal separator 41. The trace amounts of fine adsorbent components (solids) and moisture, and high-density substances such as glycerin and glycerin derivative having a specific gravity of 1 g/cm³ or higher that are contained in the light liquid that passed through the basic substance adsorption processing unit 8 are separated and removed with the centrifugal separator 41.

The low-boiling substance removal processing unit 10 comprises a static mixer-type additive introduction device 45, a reduced pressure dehydration-deodorization-deoxidation tower 44, a condenser 42, and a vacuum pump 43. The light liquid that passed through the high density substance removal processing unit 9 may be added, as needed, with additives such as the pour point depressant by the static mixer-type additive introduction device 45 before the reduced pressure dehydration-deodorization-deoxidation tower 44. Subsequently, the light liquid is introduced into the reduced pressure dehydration-deodorization-deoxidation tower 44. Here, the removal processing of low-boiling substances is performed under the conditions of 20 to 100° C., and 1 to 100 mmHg. Consequently, alcohol, moisture, odorous substances and the like are removed. Additives and the like can also be homogeneously dissolved.

The particulate/condensed substance removal processing unit 11 is configured from a cartridge-type filter 32, and a cartridge-type filter 33. The filter 32 is equipped with a 5 μm filter, and the filter 33 is equipped with a 1 μm filter, and, by sequentially passing through these filters, condensed substances of 1 μm or larger can be removed. The light liquid is transferred to a product tank after passing through the filter.

The neutralization/distillation processing unit 7 comprises, as shown in FIG. 5, a neutralization processing agitation tank 46, a dilute sulfuric acid storage tank 35, a continuous filter 36, a reduced pressure distillation tower 47, a boiler 51, a condenser 48, a vacuum pump 49, a liquid-liquid centrifugal separator 50, and a glycerin storage tank 52. The heavy liquid that was fed from the liquid-liquid separation unit 6 is foremost place into the neutralization processing agitation tank 46. Acid accumulated in the dilute acid storage tank 35 corresponding to the protons in the molar equivalent of the alkali catalyst is diluted with water having a molar equivalent of 0.3 to 5 in relation to the potassium atoms in the alkali catalyst and delivered in droplets, and neutralized while performing agitation with the agitation motor 53. Here, although the temperature of the neutralization buffer will increase due to the heat of neutralization, this is adjusted to 100° C. or less, preferably 60° C. or less with cooling water. After the delivery in droplets is complete, for example, agitation is performed for 5 to 20 minutes, and the agitation is thereafter stopped and left still for 30 minutes. Here, if a prescribed amount of water is not contained, the crystal of the potassium salt will not grow, and the solution will result in a slurry state and the filtration and removal of the subsequent step will become difficult. After confirming the generation of the potassium salt crystal, the entire liquid is passed through the continuous filter 36 from the lower drain valve. The filtrate is introduced into the distillation under reduced pressure tower 47, and distillation under reduced pressure is performed. Preferably, distillation is performed at 1 mmHg to 20 mmHg, and 160° C. to 190° C. The liquid is condensed with the condenser 48 and subject to the liquid-liquid centrifugal separator 50 in order to separate the light liquid (fatty acid alkyl ester) and the heavy liquid (glycerin).

The light liquid is returned to the basic substance adsorption processing unit 8 once again for commercialization. The heavy liquid is transferred to the glycerin storage tank 52.

EXAMPLES

The method of producing the biodiesel fuel oil is now explained with reference to specific examples.

Example 1

In the production apparatus configured as shown in FIG. 1 to FIG. 5 and having a processing/production capacity of 20 tons/day, a stainless net of 120 mesh was used as the filter to be mounted at the reception opening of the raw material oil reception tank 13. A polyester continuous fiber filter of 300 mesh was used as the filter to be mounted on the strainer 17 to be mounted on the exit side of the raw material oil storage tank 14 or the solid-liquid, liquid-liquid centrifugal separator 15.

Spent waste vegetable oil (acid value: 5.2, iodine number: 108, flash point 230° C., moisture 1.1%) that was used in restaurants and the like was received in the raw material oil reception tank 13, and then fed into the raw material oil storage tank 14. After causing the raw material oil to naturally deposit for 8 hours, the supernatant was used in the subsequent step onward. Potassium hydroxide (purity 90%) was used as the catalyst, and the catalyst dissolution bath 27 was used to dissolve the catalyst at a ratio of potassium hydroxide 8.3 parts by weight in relation to methyl alcohol (purity 99.8%) 100 parts by weight. Activated clay having an average grain size of 0.1 mm was used as the refining adsorbent of the light liquid. Sulfuric acid was used for the neutralization of the heavy liquid.

The raw material oil was passed through the strainer 17 from the raw material oil storage tank 14 via the feed pump 16, and heated to 150° C. with the multitubular heat exchanger 18. This was fed into the reduced pressure dehydration-deodorization-deoxidation tower 20. The feed speed was mass flow 20 kg/minute. The absolute pressure of the vacuum tower 20 was 5 mmHg. The acid value at this point in time was 3.1. Activated alumina (average grain size 0.1 mm, corresponding to 1 wt % in relation to the passing raw material oil) was used as the filler of the solid hydrophilic adsorbent filled column 21. The transit speed was 25 kg/minute, and the temperature of the raw material oil temperature during the passage was 80° C. The acid value at this point in time was 0.6. While confirming the mass, 1000 kg was fed into the agitation reaction tank 24 with the feed pump.

The temperature of the raw material oil in the reaction tank 24 was lowered to 64° C., and a catalyst solution was added thereto in an amount corresponding to the methanol content (121 kg, 1.1 equivalent) and the catalyst content (10 kg, 1 wt %/raw material oil). The time of delivery in droplets was 15 minutes. After the completion of the delivery in droplets, the reaction liquid was agitated for 15 minutes. The agitation speed was 360 rpm. The reaction liquid was extracted from the lower drain cock of the agitation reaction tank 24, and fed into the static specific gravity separator 30. Here, the reaction mixed liquid was left at rest for 4 hours. The lower part of the created interface; that is, the heavy liquid part having glycerin as its primary component was extracted from the drain of the static specific gravity separator 30, and then sent to the neutralization/distillation processing unit. After the heavy liquid part has been extracted, the light liquid part was sent to the basic substance adsorption processing unit 8. As the filler of the basic substance removal adsorbent filled column 31, activated carbon and activated clay were filled in a multi-layered structure. The total amount of the foregoing filler was 1% of the flow through. The transit speed was 20 liters/minute. The light liquid that passed through the column was passed through the solid-liquid separation centrifugal separator 41 at a speed of 20 liters/minute. The centrifugal effect at this time was a rotation speed corresponding to 1,000 G. The light liquid that passed through the centrifugation device was fed into the reduced pressure dehydration-deodorization-deoxidation tower 44 for removing low-boiling substances, and processed at a decompression level of 10 mmHg, temperature of 80° C., and liquid retention time of 30 minutes. After the processing, the light liquid was passed through the filters 32, 33 and fed into the product tank.

The measurement of purity of the obtained light liquid; that is, the biodiesel fuel was carried out using a capillary gas chromatograph (GC-14A, TC-1, 0.25 mmID, 15 m) and analyzed under the following conditions: inlet temperature: 280° C., detection temperature: 250° C., column temperature 40° C. 5 minutes to 320° C. 15 minutes, temperature rise speed: 10° C./minute, sample injection volume: 5 ml, and the peak area was sough with the holding time of 16 minutes to 30 minutes. With respect to the foregoing peak areas, the structure has confirmed in advance based on GC-MS. Simultaneously, the residual alcohol content and other volatile substance contents were also sought from the peak area. The moisture was sought with the Karl Fischer Moisture Titrator. The density (15° C.): [0.85 to 0.9 g/cm3], kinetic viscosity (40° C.): [1.9 to 6.0 mm2/s], 95% distillate temperature: [360° C. or less], flash point: [100° C. or higher], plugging point: [0 to −20° C. (pour point: 0 to −20° C.)], sulfur content: [200 ppm or less], residual carbon: [0.05% or less (residual carbon of 10% residual oil: 0.5% or less)], cetane number: [>51], iodine number: [120 or less], high unsaturated fatty acid (C18: 3 or higher) content: [15% or less], phosphorous content: [20 mg/kg] (reference values are indicated in []) were analyzed with the methods set forth in the JIS standard and other standard methods. The results are shown in Table 1. The conversion ratio (Conversion %) in the Tables was calculated based on the following formula. Moreover, the conversion ratio in the Tables includes the light liquid content that is collected during the refining of the heavy liquid.

Conversion ratio=created fatty acid alkyl ester content/input into the agitation reaction tank

Moreover, the heavy liquid after the liquid-liquid separation was sent to the neutralization/distillation processing unit 7 and neutralized under the following conditions.

Neutralization agent: Dilute sulfuric acid obtained from 8.0 kg of concentrated sulfuric acid+8.7 kg of water

Agitation speed of neutralization processing agitation tank 34: 100 rpm

Agitation time: 10 hours, and left at rest for 30 minutes thereafter

Temperature: 50° C.

The reaction mixed liquid (including crystals) was fed from the lower drain into the continuous filter 36. The feed speed was 10 liters/minute. After filtering the sulfuric acid potassium salt crystal, the obtained filtrate was introduced into the reduced pressure distillation tower 47 and distilled. The decompression level in the distillation was 10 mmHg, and the bottom temperature was 180° C. After removing the initial liquid partially containing moisture, the main liquid was condensed with the condenser 48, subsequently subject to the liquid-liquid centrifugal separator 50, and the light liquid having fatty acid alkyl ester as its primary component and the heavy liquid having glycerin as its primary component were separated. The heavy liquid was fed as product glycerin into the glycerin storage tank 52. The obtained light liquid was 24 kg. This was sent once again to the basic substance adsorption processing unit 8 and refined as biodiesel fuel. The BDF after independent refining was 23.8 kg. The purity of glycerin that was obtained from the heavy liquid was 99.0%, and the amount thereof was 150 kg (yield from the reaction raw material oil 95.5%).

Example 2

Other than using rapeseed oil (acid value: 0.6, iodine number: 118, flash point 230° C., moisture 0.2%) as the raw material oil, the method was performed as with Example 1. The results of the property analysis are shown in Table 1.

Example 3

Other than using soybean oil (acid value: 0.6, iodine number: 132, flash point 240° C., moisture 0.2%) as the raw material oil, the method was performed as with Example 1. The results of the property analysis are shown in Table 1.

Example 4

Other than using palm oil (acid value: 0.8, iodine number: 54, flash point 230° C., moisture 0.3%) as the raw material oil, the method was performed as with Example 1. The results of the property analysis are shown in Table 1.

Example 5

The raw material oil was fed directly from the raw material oil reception tank 13 to the liquid-liquid centrifugal separator 15 without leaving it at rest for 8 hours in the raw material oil storage tank 14, and the separation operation was subsequently performed. The temperature of the raw material oil in the foregoing case was 55° C. The raw material oil was thereafter passed through the strainer 17. The liquid transit speed was 15 liters/minute. Consequently, the time spent from receiving the raw material to reaching the reaction step was shortened to 1 hour and 30 minutes. Other than the above, the method was performed as with Example 1. The results of the property analysis are shown in Table 2.

Example 6

In the liquid-liquid separation unit 6, the reaction mixed liquid was directly sent from the reaction tank 24 to the liquid-liquid separation centrifugal separator 40. The temperature of the mixed liquid during the passage was 40° C. The transit speed was 15 liters/minute. Consequently, the retention time of the liquid-liquid separation unit was shortened to 1 hour and 30 minutes. Other than the above, the method was performed as with Example 1. The results of the property analysis are shown in Table 2.

Example 7

2,000 ppm of acrylic polymer (molecular weight 100,000) pour point depressant was added with a static mixer between the high density substance removal processing unit 9 and the low-boiling substance removal processing unit 10. Other than the above, the method was performed as with Example 1. The results of the property analysis are shown in Table 2.

Example 8

Ethyl alcohol (purity 99.5%) was used as the alcohol. Here, the reaction temperature was 75° C. Other than the above, the method was performed as with Example 1. The results of the property analysis are shown in Table 2.

Comparative Example 1

The raw material oil was passed through the strainer 17 from the raw material oil storage tank 14 via the feed pump 16, and heated to 100° C. with the multitubular heat exchanger 18. This was fed into the reduced pressure dehydration-deodorization-deoxidation tower 20. The feed speed was mass flow 20 kg/minute. The absolute pressure of the vacuum tower 20 was 5 mmHg. While confirming the mass, 1000 kg of the raw material oil was fed into the agitation reaction tank 24 with the feed pump without passing through the solid hydrophilic adsorbent filled column 21. The acid value of the raw material oil at this point in time was 3.1. Other than the above, the method was performed as with Example 1. The results of the property analysis are shown in Table 3.

Comparative Example 2

The raw material oil was passed through the strainer 17 from the raw material oil storage tank 14 via the feed pump 16, and heated to 200° C. with the multitubular heat exchanger 18. This was fed into the reduced pressure dehydration-deodorization-deoxidation tower 20. The feed speed was mass flow 20 kg/minute. The absolute pressure of the vacuum tower 20 was 5 mmHg. While confirming the mass, 1000 kg of the raw material oil was fed into the agitation reaction tank 24 with the feed pump without passing through the solid hydrophilic adsorbent filled column 21. The acid value of the raw material oil at this point in time was 0.8. Other than the above, the method was performed as with Example 1. The results of the property analysis are shown in Table 3.

Comparative Example 3

Sodium hydroxide (96.0% purity) was used in substitute for the potassium hydroxide that was used in Example 1, the catalyst was dissolved in the catalyst dissolution bath 27 at a ratio of catalyst 11.5 parts by weight in relation to methanol (purity 99.8%) 100 parts by weight, and this was placed in a prescribed amount of raw material oil and reacted. Other than the above, the method was performed as with Example 1. The results of the property analysis are shown in Table 3.

Comparative Example 4

The light liquid after the gravity separation was directly sent to the high density substance removal processing unit 9 without passing through the basic substance removal adsorbent filled column 31 of the basic substance adsorption processing unit 8. Other than the above, the method was performed as with Example 1. The results of the property analysis are shown in Table 4.

Comparative Example 5

Processing was performed without passing the raw material oil through the low-boiling substance removal processing unit 10. Other than the above, the method was performed as with Example 1. The results of the property analysis are shown in Table 4.

Comparative Example 6

Waste vegetable oil (acid value: 30, iodine number: 75, moisture 3.3%) in which the oxidation degradation has advanced considerably was used as the raw material oil. The processing conditions of the reduced pressure dehydration-deodorization-deoxidation tower 20 in the dehydration-deodorization-deoxidation unit 2 were set to 100° C. and 3 mmHg, and the transit speed was 10 liters/minute. Other than the above, the method was performed as with Example 1. The results of the property analysis are shown in Table 4.

Comparative Example 7

When neutralizing the heavy liquid that was created in the liquid-liquid separation unit 6, the sulfuric acid was not diluted with a prescribed amount of water, and the concentrated sulfuric acid (96% or more) was neutralized as is by adding a prescribed amount of neutralization agent. Here, with the mixed liquid after the neutralization, the sulfuric acid potassium salt did not separate from the system, distributed to the entire solution and become slurry with an extremely high viscosity. When this was sent as is to the reduced pressure distillation tower 37 and distilled, the glycerin yield was 63%.

TABLE 1 Example 1 Example 2 Example 3 Example 4 Reference Items UFO Rape seeds Soy beans Palm oil EN14214 1. Density 15° C. g/m³ 0.885 0.875 0.880 0.872 0.860-0.900 2. Viscosity 40° C. mm²/s 4.02 3.96 3.60 3.71 3.5-5.0 3. Flash point ° C. 140 158 159 180 >120 4. Sulfur content mg/kg 1.0 2.0 3.0 3.0 <10.0 5. Carbon residue content 0.13 0.14 0.25 0.03 <0.30 10% resid. % 6. Cetane number 53.5 52.5 51.0 55.3 >51.0 7. Sulfated ash % 0.018 0.015 0.018 0.009 <0.02 8. Water mg/kg 178 133 180 111 <500 (<200) 9. Total residue mg/kg <20 <20 <20 <20 <24 10. Copper strip corrosion <1 <1 <1 <1 <1 test 3 h, 50° C. 11. Oxidative stability 110° C. >6 (—) (—) (—) >6 12. Acid value mg KOH/g 0.3 0.2 0.2 0.3 <0.5 13. Plugging point (pour (−5.0) (−33.9) (−31.2) (+8.0) 6 grades point) ° C. 14. Methyl ester content % 99.4 99.2 99.2 99.4 >96.5 (>98.0) 15. Iodine number g 108 118 132 54 <120 Iodine/100 g 16. C18:3 or greater ratio % 4.0 9.6 7.1 0.3 <12.0 17. Methanol % 0.052 0.078 0.065 0.073 <0.20 18. Monoglyceride % 0.30 0.30 0.30 0.20 <0.80 19. Diglyceride % 0.15 0.15 0.15 0.11 <0.20 20. Triglyceride % 0.06 0.08 0.07 0.05 <0.20 21. Free glycerol % 0.005 0.005 0.005 0.005 <0.02 22. Total glycerol % 0.111 0.113 0.112 0.078 <0.25 23. Alkali metals (Na, K) <5 <5 <5 <5 <5 mg/kg 24. Alkali rare earth metals ND ND ND ND <5 (Ca, Mg) 25. Phosphorus mg/kg 5 5 3 8 <10.0 26. Conversion ratio % 99.5 99.6 99.6 99.6 — 27. Rate of glycerol 95.5 96.4 96.2 96.6 — production % Figures in ( ) of EN14214 represent the standard value expected for the ensuing term.

TABLE 2 Example 5 Example 6 Example 7 Example 8 Reference Items UFO UFO UFO UFO EN14214 1. Density 15° C. g/m³ 0.885 0.885 0.889 0.884 0.860-0.900 2. Viscosity 40° C. mm²/s 4.15 4.13 4.90 4.96 3.5-5.0 3. Flash point ° C. 140 141 140 153 >120 4. Sulfur content mg/kg 1.0 1.0 1.0 1.0 <10.0 5. Carbon residue content 0.20 0.20 0.26 0.13 <0.30 10% resid. % 6. Cetane number 53.5 53.5 53.9 59.0 >51.0 7. Sulfated ash % 0.018 0.018 0.019 0.018 <0.02 8. Water mg/kg 180 180 170 178 <500 (<200) 9. Total residue mg/kg <20 <20 — <20 <24 10. Copper strip corrosion <1 <1 <1 <1 <1 test 3 h, 50° C. 11. Oxidative stability 110° C. >6 >6 >6 >6 >6 12. Acid value mg KOH/g 0.3 0.4 0.3 0.3 <0.5 13. Plugging point (pour (−4.5) (−4.5) (−20.0) (−8.0) 6 grades point) ° C. 14. Methyl ester content % 99.3 99.3 99.0 (99.4) >96.5 (>98.0) Ethyl 15. Iodine number g 108 108 108 106 <120 Iodine/100 g 16. C18:3 or greater ratio % 4.0 4.0 4.0 3.9 <12.0 17. Methanol % 0.055 0.065 0.050 0.050 <0.20 18. Monoglyceride % 0.30 0.30 0.30 0.30 <0.80 19. Diglyceride % 0.15 0.15 0.15 0.15 <0.20 20. Triglyceride % 0.08 0.07 0.06 0.06 <0.20 21. Free glycerol % 0.005 0.005 0.005 0.005 <0.02 22. Total glycerol % 0.113 0.112 0.111 0.111 <0.25 23. Alkali metals (Na, K) <5 <5 <5 <5 <5 mg/kg 24. Alkali rare earth metals ND ND ND ND <5 (Ca, Mg) 25. Phosphorus mg/kg 5 5 5 5 <10.0 26. Conversion ratio % 99.5 99.4 99.5 99.8 — 27. Rate of glycerol 95.5 95.2 95.6 95.5 — production % Figures in ( ) of EN14214 represent the standard value expected for the ensuing term.

TABLE 3 Comparative Comparative Comparative Example 1 Example 2 Example 3 Reference Items UFO UFO UFO EN14214 1. Density 15° C. g/m³ 0.890 0.895 0.889 0.860-0.900 2. Viscosity 40° C. mm²/s 5.12 6.00 6.12 3.5-5.0 3. Flash point ° C. 148 151 166 >120    4. Sulfur content mg/kg 1.0 1.0 1.0 <10.0  5. Carbon residue content 0.35 0.50 0.86 <0.30 10% resid. % 6. Cetane number 51.5 52.5 51.0 >51.0  7. Sulfated ash % 0.028 0.038 0.039 <0.02 8. Water mg/kg 250 260 1200 <500    (<200)    9. Total residue mg/kg 25 38 55 <24    10. Copper strip corrosion <1 <1 <1 <1   test 3 h, 50° C. 11. Oxidative stability >6 >6 >6 >6   110° C. 12. Acid value mg KOH/g 0.8 0.4 0.7 <0.5  13. Plugging point (pour (−1.5) (+1.6) (−2.0) 6 grades point) ° C. 14. Methyl ester content % 98.8 98.5 96.5 >96.5  (>98.0)  15. Iodine number g 108 108 108 <120    Iodine/100 g 16. C18:3 or greater 4.0 2.3 4.0 <12.0  ratio % 17. Methanol % 0.055 0.065 0.080 <0.20 18. Monoglyceride % 0.60 0.90 0.60 <0.80 19. Diglyceride % 0.30 0.45 0.30 <0.20 20. Triglyceride % 0.16 0.21 0.12 <0.20 21. Free glycerol % 0.010 0.015 0.010 <0.02 22. Total glycerol % 0.226 0.336 0.222 <0.25 23. Alkali metals (Na, K) <5 <5 <5 <5   mg/kg 24. Alkali rare earth metals ND ND ND <5   (Ca, Mg) 25. Phosphorus mg/kg 5 5 5 <10.0  26. Conversion ratio % 97.5 97.8 91.3 — 27. Rate of glycerol 93.0 92.0 88.0 — production % Figures in ( ) of EN14214 represent the standard value expected for the ensuing term.

TABLE 4 Comparative Comparative Comparative Example 4 Example 5 Example 6 Reference Items UFO UFO UFO EN14214 1. Density 15° C. g/m³ 0.910 0.874 0.895 0.860-0.900 2. Viscosity 40° C. mm²/s 7.12 4.00 6.35 3.5-5.0 3. Flash point ° C. 153 110 150 >120    4. Sulfur content mg/kg 1.0 1.0 1.0 <10.0  5. Carbon residue content 0.69 0.20 0.30 <0.30 10% resid. % 6. Cetane number 50.5 51.0 51.0 >51.0  7. Sulfated ash % 0.068 0.018 0.018 <0.02 8. Water mg/kg 480 550 380 <500    (<200)    9. Total residue mg/kg 55 28 100 <24    10. Copper strip corrosion 2 <1 2 <1   test 3 h, 50° C. 11. Oxidative stability 6 >6 4 >6   110° C. 12. Acid value mg KOH/g 0.3 0.2 0.2 <0.5  13. Plugging point (pour (+1.5) (−1.5) (+8.0) 6 grades point) ° C. 14. Methyl ester content % 97.8 98.5 95.0 >96.5  (>98.0)  15. Iodine number g 108 108 106 <120    Iodine/100 g 16. C18:3 or greater 4.0 4.0 4.0 <12.0  ratio % 17. Methanol % 0.055 0.500 0.050 <0.20 18. Monoglyceride % 0.60 0.30 0.90 <0.80 19. Diglyceride % 0.30 0.15 0.45 <0.20 20. Triglyceride % 0.16 0.07 0.21 <0.20 21. Free glycerol % 0.010 0.005 0.015 <0.02 22. Total glycerol % 0.226 0.111 0.336 <0.25 23. Alkali metals (Na, K) 18 <5 8 <5   mg/kg 24. Alkali rare earth metals ND ND ND <5   (Ca, Mg) 25. Phosphorus mg/kg 5 5 5 <10.0  26. Conversion ratio % 98.5 99.1 81.0 — 27. Rate of glycerol 95.5 95.5 75.0 — production % Figures in ( ) of EN14214 represent the standard value expected for the ensuing term.

As evident from the Tables, even when using degraded oils and fats in which values such as the pour point and iodine number that depend on the raw material oils and fats do not satisfy the standard value, according to the production method pertaining to the present invention, it has been confirmed that a high quality biodiesel fuel that satisfies the other standard values can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an example of an apparatus for implementing the method of producing a biodiesel fuel oil according to the present invention;

FIG. 2 is a is a schematic diagram showing the configuration of a pretreatment unit, a dehydration-deodorization-deoxidation unit, and an acidic substance removal processing unit that configure a part of the production apparatus illustrated in FIG. 1;

FIG. 3 is a schematic diagram showing the configuration of a catalyst-containing alcohol solution preparation unit, a mixed reaction unit, and a liquid-liquid separation unit that configure a part of the production apparatus illustrated in FIG. 1;

FIG. 4 is a schematic diagram showing the configuration of a basic substance adsorption processing unit, a high density substance removal processing unit, a low-boiling substance removal processing unit, and a particulate/condensed substance removal processing unit that configure a part of the production apparatus illustrated in FIG. 1; and

FIG. 5 is a schematic diagram configuring a neutralization/distillation processing unit that configures a part of the production apparatus illustrated in FIG. 1.

EXPLANATION OF REFERENCE NUMERALS

1 . . . pretreatment unit, 2 . . . dehydration-deodorization-deoxidation unit, 3 . . . acidic substance removal processing unit, 4 . . . catalyst-containing alcohol solution preparation unit, 5 . . . mixed reaction unit, 6 . . . liquid-liquid separation unit, 7 . . . neutralization/distillation processing unit, 8 . . . basic substance adsorption processing unit, 9 . . . high density substance removal processing unit, 10 . . . low-boiling substance removal processing unit, 11 . . . particulate/condensed substance removal processing unit, 13 . . . raw material oil reception tank, 14 . . . raw material oil storage tank, 15, 40, 41, 50 . . . centrifugal separator, 17 . . . strainer with cartridge filter, 18 . . . multitubular heat exchanger, 19, 51 . . . boiler, 20 . . . reduced pressure dehydration-deodorization-deoxidation tower, 21 . . . solid hydrophilic adsorbent filled column, 22, 42, 48 . . . condenser, 23, 43, 49 . . . vacuum pump, 24 . . . agitation reaction tank, 25, 53 . . . agitation motor, 26 . . . agitating blade, 27 . . . catalyst dissolution bath, 29 . . . alcohol storage tank, 30 . . . static specific gravity separator, 31 . . . basic substance removal adsorbent filled column, 32, 33 . . . cartridge-type filter, 35 . . . dilute acid storage tank, 36 . . . continuous filter, 47 . . . reduced pressure distillation tower neutralization processing agitation tank, 45 . . . static mixer-type additive introduction device, 52 . . . glycerin storage tank 

1. A method of producing a biodiesel fuel from a raw material oil having an acid value of 20 or less, comprising: a step of heating the raw material oil under reduced pressure to distill and remove moisture, odorous substances and free fatty acids; a step of causing the raw material oil to come in contact with a hydrophilic adsorbent to adsorb and remove residual free fatty acids and acidic substances; a step of subjecting the raw material oil and alcohol to an ester exchange reaction in the presence of an alkali catalyst of at least one type selected from a group including potassium hydroxide, potassium carbonate, and potassium alcoholate; a step of separating light liquid components from a reaction product resulting from the ester exchange reaction; and a step of performing, to the light liquid components, processing of causing the light liquid components to come in contact with a basic substance adsorptive solid adsorbent, processing of removing solid impurities and the like by way of centrifugation, processing of heating the light liquid components under reduced pressure to remove low-boiling substances, and processing of removing solid impurities and the like through a filter.
 2. The method of producing a biodiesel fuel according to claim 1, wherein the hydrophilic adsorbent is at least one type selected from a group including activated alumina, basic-treated activated carbon, and silica gel.
 3. The method of producing a biodiesel fuel according to claim 1, wherein the ester exchange reaction step includes: a step of preparing a catalyst-containing alcohol solution by dissolving the alkali catalyst which is 0.5 wt % in relation the raw material oil, in alcohol which is 1.05 to 1.25 molar equivalent in relation to a fatty acid moiety of the raw material oil; and a step of mixing and agitating the raw material oil and the catalyst-containing alcohol solution.
 4. The method of producing a biodiesel fuel according to claim 1, wherein the step of separating the light liquid components is performed by subjecting the reaction product to centrifugation.
 5. The method of producing a biodiesel fuel according to claim 1, wherein the basic substance adsorptive solid adsorbent is at least one type selected from a group including activated clay, acid clay, activated carbon, bentonite, silica gel, activated alumina, and molecular sieves.
 6. The method of producing a biodiesel fuel according to claim 1, wherein a pour point depressant and an oxidation stabilizer are added to the light liquid before performing the processing of heating the light liquid components under reduced pressure to remove low-boiling substances.
 7. The method of producing a biodiesel fuel according to claim 1, wherein, prior to performing the distillation and removal step, performed are: a step of gravity-separating water or an aqueous solution from the raw material oil; and a step of removing solid substances from the gravity-separated raw material oil with a filter.
 8. The method of producing a biodiesel fuel according to claim 1, wherein the alcohol used in the ester exchange reaction is at least one type selected from a group including methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, and t-butyl alcohol.
 9. The method of producing a biodiesel fuel according to claim 1, further comprising: a step of diluting sulfuric acid or phosphoric acid corresponding to protons of an equivalent mole in relation to an alkali catalyst with water having a molar equivalent of 0.3 to 5 in relation to potassium atoms in the alkali catalyst and adding the product to and neutralizing heavy liquid components after the light liquid components are separated from the reaction product; and a step of distilling under reduced pressure a filtrate remaining after filtrating and removing the obtained clathrate hydrate, or a hydrated potassium sulphate crystal or a hydrated tripotassium phosphate crystal, and obtaining glycerin as a by-product. 